29 Si spin‐lattice NMR relaxation in microporous silica‐based materials with high Mn 2+ concentrations

• Published in: Magnetic resonance in chemistry 2006-11, Vol.44 (11), p.985-988
• Main Authors: Bakhmutov, Vladimir I., Shpeizer, Boris G., Clearfield, Abraham
• Format: Article
• Language: English
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.1899

The 29 Si T 1 time measurements have been performed under magic angle spinning for supermicroporous Si/Mn materials 1–6 containing Mn 2+ in concentrations of 0 (1), 1.2 (2), 2.5 (3), 3.8 (4), 15 (5) and 19.8 wt% (6). It has been found that the central lines, corresponding to isotropic chemical shifts, and their sidebands relax differently in samples 2–4 with relatively small Mn 2+ contents. Because the relaxation curves for 1–6 are nonexponential and identical for 6 at spinning rates of 5, 10 and 12 kHz, dipolar relaxation via the paramagnetic centers is dominant. The relaxation data have been interpreted as a function of Mn 2+ concentrations in terms of incorporation of the Mn 2+ ions into the silica lattice when their concentration is small (≤2.5 wt%). At higher concentrations, most of the manganese is located on the surface of the silica. Copyright © 2006 John Wiley & Sons, Ltd.